Lubricating oil supply structure

ABSTRACT

A housing supporting a rotational shaft and accommodating an axial piston member is provided with an oil reservoir space that faces at least one of the two end faces in the axial direction of the rotational shaft. The rotational shaft is provided with a rotational-shaft-side supply oil passage that includes an axial hole open to the oil reservoir space and an axial-piston-member lubricating oil hole having one end fluidly connected to the axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the axial piston member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricating oil supply structure applied to an axial piston device in which axial piston members such as a hydraulic pump and a hydraulic motor are accommodated in a housing with being supported by a rotational shaft.

2. Background Art

An axial piston device including a rotational shaft, an axial piston member such as a hydraulic pump or a hydraulic motor supported by the rotational shaft, and a housing supporting the rotational shaft and accommodating the axial piston member is widely used as, for example, a hydrostatic transmission (HST) disposed in a drive-line power transmission passage in a working vehicle.

In the axial piston device, it is necessary to reduce wear by supplying lubricating oil to portions of the axial piston member where slide contact occurs, and in general, lubricating oil is supplied to the slide contact portions via an axial hole formed in the rotational shaft.

Meanwhile, in conventional axial piston devices, lubricating oil is supplied to the axial hole of the rotational shaft due to the following configuration.

That is, the rotational shaft is supported in a rotatable manner around an axis line, directly or via a bearing member, by a bearing hole formed in the housing.

Lubricating oil is supplied to the axial hole of the rotational shaft via: a lubricating-oil-supply oil passage formed in the housing such that the first end side is fluidly connected to the source of the lubricating oil and the second end side opens to the bearing hole, a rotary joint formed on the outer circumferential surface of the rotational shaft so as to face the opening on the second end side of the lubricating-oil-supply oil passage, and a communicating oil passage formed in the rotational shaft such that the outer end is fluidly connected to the rotary joint and the inner end is fluidly connected to the axial hole.

According to the foregoing configuration, the communicating oil passage is always fluidly connected to the lubricating-oil-supply oil passage via the rotary joint irrespective of the state of axial rotation of the rotational shaft, and, theoretically, lubricating oil is invariably supplied to the axial hole.

However, centrifugal force acts in the radially outward direction on the communicating oil passage as the rotational shaft axially rotates.

The direction of this centrifugal force is opposite to the flow direction of lubricating oil that flows toward the inner end from the outer end of the communicating oil passage in order for the lubricating oil from the lubricating-oil-supply oil passage to be sent to the axial hole, and thus the centrifugal force interferes with the flow of the lubricating oil in the communicating oil passage.

BRIEF SUMMARY OF THE INVENTION

The present invention has been conceived in view of the above-described conventional art, and an object of the present invention is to provide a lubricating oil supply structure applicable to an axial piston device including a rotational shaft, an axial piston member supported by the rotational shaft and a housing supporting the rotational shaft and accommodating the axial piston member, the lubricating oil supply structure capable of effectively supplying lubricating oil to the axial piston device supported by the rotational shaft.

In order to achieve the object, the present invention provides a lubricating oil supply structure applicable to an axial piston device including a rotational shaft, an axial piston member supported by the rotational shaft in a relatively non-rotatable manner with respect thereto and a housing accommodating the axial piston member wherein the rotational shaft supports the axial piston device at a central part in an axial direction and is supported at one end side and the other end side in the axial direction by first-end-side and second-end-side bearing holes formed in the housing in a rotatable manner around the axis line, the lubricating oil supply structure including an oil reservoir space formed in the housing so as to be capable of receiving oil from an oil source and face at least one of the two end faces in the axial direction of the rotational shaft, and a rotational-shaft-side supply oil passage that is formed in the rotational shaft, wherein the rotational-shaft-side supply oil passage has an axial hole open to an end face of the rotational shaft that faces the oil reservoir space among the two end faces in the axial direction of the rotational shaft and an axial-piston-member lubricating oil hole having one end fluidly connected to the axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the axial piston member.

Since the housing that supports the rotational shaft and accommodates the axial piston member is provided with the oil reservoir space facing at least one end face of the rotational shaft, and the rotational shaft is provided with the rotational-shaft-side supply oil passage including the axial hole open to the oil reservoir space and the axial-piston-member lubricating oil hole that has one end fluidly connected to the axial hole and the other end open to the portion of the external surface of the first rotational shaft, the portion facing the axial piston member, the lubricating oil supply structure according to the present invention makes it possible to effectively prevent centrifugal force, which is caused by the axial rotation of the rotational shaft around the axis line, from interfering the flow of the lubricating oil toward the axial piston device, thereby smoothly guiding lubricating oil to the axial piston device.

Preferably, the rotational-shaft-side supply oil passage may have a lubricating oil hole for bearing member having one end fluidly connected to the axial hole and the other end open to at least one of portions of the external surface of the rotational shaft that are located in the first- and second-end-side bearing holes, respectively.

More preferably, the lubricating oil hole for bearing member may include a first-end-side lubricating oil hole that is fluidly connected to the axial hole and open to the portion of the external surface of the rotational shaft located in the first-end-side bearing hole, and a second-end-side lubricating oil hole that is fluidly connected to the axial hole and open to the portion of the external surface of the rotational shaft located in the second-end-side bearing hole.

In a configuration in which the rotational shaft includes first and second rotational shafts coaxially disposed to each other and the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, the first and second rotational shafts may be disposed such that there is a gap between the end face on the first end side of the first rotational shaft and the end face on the second end side of the second rotational shaft.

In the case, the gap may be used as the oil reservoir space, the axial hole may include first and second axle holes that are fluidly connected to the oil reservoir space and formed in the first and second rotational shafts, respectively, and the axial-piston-member lubricating oil hole may include a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member, and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.

In the configuration in which the first and second rotational shafts are disposed coaxially to each other, the housing preferably may have a port block including the reservoir space, a first housing body removably connected to the port block to form a first accommodating space accommodating the first axial piston member, and a second housing body removably connected to the port block to form a second accommodating space that is positioned opposite to the first accommodating space with reference to the port block and accommodates the second axial piston member.

In a configuration in which the rotational shaft includes first and second rotational shafts arranged parallel to each other to have axis lines mutually displaced and the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, the housing may be preferably provided with a first oil reservoir space that is capable of receiving an oil from the oil source and faces at least one of the end faces on one side and the other side in the axis direction of the first rotational shaft and a second oil reservoir space that is capable of receiving an oil from the oil source and faces at least one of the end faces on one side and the other side in the axis direction of the second rotational shaft, as the oil reservoir space.

In the case, the axial hole may include a first axle hole formed in the first rotational shaft so as to be fluidly connected to the first oil reservoir space and a second axle hole formed in the second rotational shaft so as to be fluidly connected to the second oil reservoir space, and the axial-piston-member lubricating oil hole may include a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.

In the configuration in which the first and second rotational shafts are arranged parallel to each other to have axis lines displaced from each other, the housing may include a port block and a housing body removably connected to the port block to form an accommodating space accommodating the first and second axial piston members.

In a configuration in which the first rotational shaft functions as a pump shaft that is operatively connected to a driving source and the second rotational shaft functions as a motor shaft that outputs rotative power, and at least one of the first axial piston member functioning as a hydraulic pump and the second axial piston member functioning as a hydraulic motor is a variable-volume type, the housing may be formed with a pair of hydraulic oil passages that fluidly connects the first and second axial piston members so as to form a closed circuit including them and a charge oil passage for replenishing the closed circuit with hydraulic oil. In the case, a part of oil in the charge oil passage may be preferably supplied to the oil reservoir space.

In the configuration in which the axial piston member includes the first and second axial piston members, the first axial piston member may include a first cylinder block supported by the first rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the first rotational shaft, and a plurality of first pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of first pistons being directly or indirectly come into contact with a first swash plate provided in the first axial piston device to define the volume of the first axial piston member, and the second axial piston member may include a second cylinder block supported by the second rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the second rotational shaft, and a plurality of second pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of second pistons being directly or indirectly come into contact with a second swash plate provided in the second axial piston device to define the volume of the second axial piston member.

In the case, the other end of the first-axial-piston-member lubricating oil hole may be preferably open to a portion of the external surface of the first rotational shaft that is close to a region where the free ends of the plurality of first pistons are come into contact with the first movable swash plate, and the other end of the second-axial-piston-member lubricating oil hole may be preferably open to a portion of the external surface of the second rotational shaft that is close to a region where the free ends of the plurality of second pistons are come into contact with the second movable swash plate.

In a case in which the first swash plate is a movable swash plate including a base portion supported by the housing in a rotatable manner around a rocking axis perpendicular to the first rotational shaft, and a swash plate body supported by the base portion and directly or indirectly engaged with the free ends of the plurality of first pistons, the housing is further provided with a lubricating oil hole for the first swash plate having one end side fluidly connected to the oil source and the other end side open to a supporting hole that is formed in the housing so as to support the base portion.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The above, and other objects, features and advantages of the present invention will become apparent from the detailed description thereof in conjunction with the accompanying drawings therein.

FIG. 1 is a vertical cross-sectional view of one example of an axial piston device to which a lubricating oil supply structure according to one embodiment of the present invention is applied.

FIG. 2 is a partial cross-sectional view taken along the line II-II in FIG. 1.

FIG. 3 is a hydraulic circuit diagram of the axial piston device shown in FIG. 1.

FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 1.

FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 1.

FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 2.

FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 2.

FIG. 8 is a partially enlarged view of FIG. 4.

FIG. 9 is a vertical cross-sectional view of a first modification of the axial piston device shown in FIG. 1.

FIG. 10 is a partially enlarged view of FIG. 9.

FIG. 11 is a partially enlarged cross-sectional view of a second modification of the axial piston device shown in FIG. 1.

FIG. 12 is a partially enlarged cross-sectional view of a third modification of the axial piston device shown in FIG. 1.

FIG. 13 is a vertical cross-sectional view of one example of an axial piston device to which a lubricating oil supply structure according to another embodiment of the present invention is applied.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

Below, one embodiment of a lubricating oil supply structure according to the present invention will now be described with reference to the appended drawings.

FIG. 1 shows a vertical cross-sectional view of one example 1A of an axial piston device to which a lubricating oil supply structure according to the present embodiment is applied.

FIG. 2 shows a partial cross-sectional view taken along the line II-II in FIG. 1.

FIG. 3 shows a hydraulic circuit diagram of the axial piston device 1A.

First, the axial piston device 1A will now be described.

As shown in FIG. 1, the axial piston device 1A has a rotational shaft 50, an axial piston member 60 supported by the rotational shaft 50 in a relatively non-rotatable manner with respect thereto, and a housing 10 supporting the rotational shaft 50 and accommodating the axial piston member 60.

As shown in FIGS. 1 to 3, the axial piston device 1A has first and second rotational shafts 50(1) and 50(2) as the rotational shaft 50 and first and second axial piston members 60(1) and 60(2) as the axial piston member 60.

While the first and second rotational shafts 50(1) and 50(2) respectively support the corresponding axial piston members 60(1) and 60(2) at the central parts in the axial direction, both ends are supported by the housing 10 in a rotatable manner around the axis line.

In the present embodiment, the first and second rotational shafts 50(1) and 50(2) are coaxially disposed as shown in FIG. 1.

Specifically, the first rotational shaft 50(1) has a first end side 50 a(1) on one end side in the axial direction and a second end side 50 b(1) on the other end side in the axial direction.

Likewise, the second rotational shaft 50(2) has a first end side 50 a(2) on one end side in the axial direction and a second end side 50 b(2) on the other end side in the axial direction.

The first and second rotational shafts 50(1) and 50(2) are coaxially disposed, with the end face on the first end side 50 a(1) of the first rotational shaft 50(1) and the end face on the second end side 50 b(2) of the second rotational shaft 50(2) facing each other.

More specifically, in the present embodiment, the housing 10 is formed with a first-rotational-shaft first-end-side bearing hole 18 a(1) and a first-rotational-shaft second-end-side bearing hole 18 b(1) capable of respectively supporting the first end side 50 a(1) and the second end side 50 b(1) of the first rotational shaft 50(1) in a rotatable manner around the axis line via bearing members 55 a(1) and 55 b(1), and a second-rotational-shaft first-end-side bearing hole 18 a(2) and a second-rotational-shaft second-end-side bearing hole 18 b(2) capable of respectively supporting the first end side 50 a(2) and the second end side 50 b(2) of the second rotational shaft 50(2) in a rotatable manner around the axis line via bearing members 55 a(2) and 55 b(2).

As shown in FIG. 1, in the present embodiment, the housing 10 has a port block 20 in which the first-rotational-shaft first-end-side bearing hole 18 a(1) and the second-rotational-shaft second-end-side bearing hole 18 b(2) are formed, a first housing body 15(1) removably connected to the port block 20 to form a first accommodating space accommodating the first axial piston member 60(1), and a second housing body 15(2) removably connected to the port block 20 to form a second accommodating space accommodating the second axial piston member 60(2).

Reference number 11 in FIGS. 1 and 3 indicates a drain port for discharging the oil retained in the first and second accommodating spaces to the outside.

As shown in FIG. 1, the first housing body 15(1) has a hollow first peripheral wall 16(1) surrounding the first axial piston member 60(1) and a first end wall 17(1) blocking the end of the first peripheral wall 16(1) on the side opposite to the port block 20, and a side of the first peripheral wall 16(1) that is close to the port block 20 is configured to be an opening into which the first axial piston member 60(1) can be inserted.

In this configuration, the first-rotational-shaft second-end-side bearing hole 18 b(1) is formed in the first end wall 17(1).

Likewise, as shown in FIG. 1, the second housing body 15(2) has a hollow second peripheral wall 16(2) surrounding the second axial piston member 60(2) and a second end wall 17(2) blocking the end of the second peripheral wall 16(2) on the side opposite to the port block 20, and a side of the second peripheral wall 16(2) that is close to the port block 20 is configured to be an opening into which the second axial piston member 60(2) can be inserted.

In this configuration, the second-rotational-shaft first-end-side bearing hole 18 a(2) is formed in the second end wall 17(2).

The axial piston device 1A is configured to function as a hydrostatic transmission (HST).

That is, the first rotational shaft 50(1) functions as a pump shaft that is operatively connected to a driving source 900 (see FIG. 3), and the second rotational shaft 50(2) functions as a motor shaft that outputs rotative power.

The first axial piston member 60(1) that is supported by the first rotational shaft 50(1) and functions as a hydraulic pump and the second axial piston member 60(2) that is supported by the second rotational shaft 50(2) and functions as a hydraulic motor, at least one of which is a variable-volume type, are fluid-connected to each other by a pair of hydraulic oil lines 100 (see FIG. 3) so as to form a closed circuit.

As shown in FIGS. 1 to 3, the axial piston device 1A further has a first swash plate 70(1) defining the volume of the first axial piston member 60(1) and a second swash plate 70(2) defining the volume of the second axial piston member 60(2).

In the present embodiment, the first swash plate 70(1) is a movable swash plate capable of tilting around a rocking axis R (see FIG. 2) based on external operation, so that the volume of the first axial piston member 60(1) that functions as a hydraulic pump is variable.

Here, a lubricating oil supply structure according to the present embodiment will now be described.

The lubricating oil supply structure guides oil from an oil source to the axial piston member 60 (the first and second axial piston members 60(1) and 60(2) in the present embodiment), and has an oil reservoir space 200 that is capable of receiving oil from the oil source and that is formed in the housing 10 so as to face at least one of the two end faces in the axial direction of the rotational shaft 50, and a rotational-shaft-side supply oil passage 210 that is formed in the rotational shaft 50.

As described above, in the present embodiment, the axial piston device 1A has the first and second rotational shafts 50(1) and 50(2) as the rotational shaft 50.

In this configuration, the oil reservoir space 200 faces at least one of the two end faces in the axial direction of the first rotational shaft 50(1) and at least one of the two end faces in the axial direction of the second rotational shaft 50(2).

In the present embodiment, the oil reservoir space 200 is a single space mutually applied to both the first and second rotational shafts 50(1) and 50(2).

Specifically, as shown in FIG. 1, the first and second rotational shafts 50(1) and 50 (2) are coaxially disposed such that there is a gap between the end face on the first end side 50 a(1) of the first rotational shaft 50(1) and the end face on the second end side 50 b(2) of the second rotational shaft 50(2), and the gap is used as the oil reservoir space 200.

Preferably, as shown in FIG. 1, seal rings are each provided on the external surface on the first end side 50 a(1) of the first rotational shaft 50(1) and the external surface on the second end side 50 b(2) of the second rotational shaft 50(2), and oil leakage from the oil reservoir space 200 is prevented by the seal rings.

In a case where the first and second rotational shafts 50(1) and 50(2) are provided as the rotational shaft 50 as in the present embodiment, the rotational-shaft-side supply oil passage 210 includes first- and second-rotational-shaft-side supply oil passages 210(1) and 210(2) formed in the first and second rotational shaft 50(1) and 50(2), respectively.

As shown in FIGS. 1 and 2, the first-rotational-shaft-side supply oil passage 210(1) has a first axial hole 215(1) open to the end face facing the oil reservoir space 200 among the two end faces in the axial direction of the first rotational shaft 50(1) (the end face on the first end side 50 a(1) of the first rotational shaft 50(1) in the present embodiment) and a first-axial-piston-member lubricating oil hole 220(1) having one end fluidly connected to the first axial hole 215(1) and the other end open to a portion of the external surface of the first rotational shaft 50(1) that faces the first axial piston member 60(1).

Likewise, the second-rotational-shaft-side supply oil passage 210(2) has a second axial hole 215(2) open to the end face facing the oil reservoir space 200 among the two end faces in the axial direction of the second rotational shaft 50(2) (the end face on the second end side 50 b(2) of the second rotational shaft 50(2) in the present embodiment) and a second-axial-piston-member lubricating oil hole 220(2) having one end fluidly connected to the second axial hole 215(2) and the other end open to a portion of the external surface of the second rotational shaft 50(2) that faces the second axial piston member 60(2).

As explained above, in the lubricating oil supply structure according to the present embodiment, the oil reservoir space 200 to which oil from an oil source is supplied is provided in the housing 10, the rotational shaft 50 supporting the axial piston member 60 is disposed such that at least one end face among the two end faces in the axial direction of the rotational shaft 50 faces the oil reservoir space 200, and, furthermore, the rotational shaft 50 is provided with the rotational-shaft-side supply oil passage 210 including the axial hole 215 open to the end face facing the oil reservoir space 200 and the axial-piston-member lubricating oil hole 220 having one end fluidly connected to the axial hole 215 and the other end open to the portion of the external surface of the rotational shaft 50 that faces the axial piston member 60. It is therefore possible to allow oil to smoothly flow from the oil source to the axial hole 215, and it is possible to efficiently supply lubricating oil to the axial piston member 60.

Specifically, in a conventional axial piston device including a rotational shaft, an axial piston member supported by the rotational shaft, and a housing supporting the rotational shaft and accommodating the axial piston member, lubricating oil is supplied from a lubricating-oil-supply oil passage formed in the housing to an axial hole formed in the rotational shaft via a rotary joint formed on the external surface of the rotational shaft and a communicating oil passage formed in the rotational shaft such that the outer end is fluidly connected to the rotary joint and the inner end is fluidly connected to the axial hole.

This configuration ensures that the axial hole is always fluidly connected to the lubricating-oil-supply oil passage via the rotary joint irrespective of the state of axial rotation of the rotational shaft, and, theoretically, the lubricating oil is invariably supplied to the axial hole from the lubricating-oil-supply oil passage.

However, centrifugal force acts in the radially outward direction on the communicating oil passage in accordance with the axial rotation of the rotational shaft.

The direction of this centrifugal force is opposite to the flow direction of lubricating oil that should flow toward the inner end from the outer end of the communicating oil passage, interfering with the flow of the lubricating oil in the communicating oil passage.

On the other hand, in the present embodiment, the axial hole 215 formed in the rotational shaft 50 is open to the end face facing the oil reservoir space 200, lubricating oil flows into the axial hole 215 from the oil reservoir space 200, and, thereafter, the lubricating oil flows radially outward through the axial-piston-member lubricating oil hole 220 from the axial hole 215.

Therefore, centrifugal force caused by the axial rotation of the rotational shaft 50 does not interfere with the flow of lubricating oil, and the lubricating oil is allowed to smoothly flow to the axial piston member 60.

In the present embodiment, the first axial piston member 60(1) includes a first cylinder block 61(1) supported by the first rotational shaft 50(1) in a relatively non-rotatable manner with respect thereto and has a plurality of cylinder holes arranged around the axis line of the first rotational shaft 50(1), and a plurality of first pistons 62(1) accommodated in the plurality of the cylinder holes in a reciprocating manner. In the configuration, the first-axial-piston-member lubricating oil hole 220(1) is formed so as to be capable of supplying lubricating oil to the region where the free ends of the plurality of first pistons 62(1) are come into contact with the first movable swash plate 70(1).

Likewise, the second axial piston member 60(2) includes a second cylinder block 61(2) supported by the second rotational shaft 50(2) in a relatively non-rotatable manner with respect thereto and has a plurality of cylinder holes arranged around the axis line of the second rotational shaft 50(2), and a plurality of second pistons 62(2) accommodated in the plurality of the cylinder holes in a reciprocating manner.

In the configuration, the second-axial-piston-member lubricating oil hole 220(2) is formed so as to be capable of supplying lubricating oil to the region where the free ends of the plurality of second pistons 62(2) are come into contact with the second movable swash plate 70(2).

The lubricating oil supply structure according to the present embodiment is configured to supply lubricating oil also to bearing portions of the rotational shaft 50.

Specifically, the first-rotational-shaft-side supply oil passage 210(1) further has a first-end-side lubricating oil hole 225 a(1) having one end fluidly connected to the first axial hole 215(1) and the other end open to a portion of the external surface of the first rotational shaft 50(1) located in the first-rotational-shaft first-end-side bearing hole 18 a(1) and a second-end-side lubricating oil hole 225 b(1) having one end fluidly connected to the first axial hole 215(1) and the other end open to a portion of the external surface of the first rotational shaft 50(1) located in the first-rotational-shaft second-end-side bearing hole 18 b(1).

According to this configuration, lubricating oil can be efficiently supplied to the bearing members 55 a(1) and 55 b(1) respectively supporting the first and second end sides 50 a(1) and 50 b(1) of the first rotational shaft 50(1).

Likewise, the second-rotational-shaft-side supply oil passage 210(2) further has a first-end-side lubricating oil hole 225 a(2) having one end fluidly connected to the second axial hole 215(2) and the other end open to a portion of the external surface of the second rotational shaft 50(2) located in the second-rotational-shaft first-end-side bearing hole 18 a(2) and a second-end-side lubricating oil hole 225 b(2) having one end fluidly connected to the second axial hole 215(2) and the other end open to a portion of the external surface of the second rotational shaft 50(2) located in the second-rotational-shaft second-end-side bearing hole 18 b(2).

According to this configuration, lubricating oil can be efficiently supplied to bearing members 55 a(2) and 55 b(2) respectively supporting the first and second end sides 50 a(2) and 50 b(2) of the second rotational shaft 50(2).

Here, the oil source for the lubricating oil supply structure will now be described.

As described above, in the present embodiment, the axial piston device 1A functions as a hydrostatic transmission (HST).

In this configuration, the lubricating oil supply structure uses oil in the charge line 110 of the hydrostatic transmission as the oil source.

Specifically, as shown in FIG. 3, the first axial piston member 60(1) that functions as a hydraulic pump and the second axial piston member 60(2) that functions as a hydraulic motor are fluidly connected by the pair of hydraulic oil lines 100, and the pair of hydraulic oil lines 100 are replenished with hydraulic oil via the charge line 110.

FIGS. 4 and 5 show cross-sectional views taken along the lines IV-IV and V-V in FIG. 1, respectively.

FIGS. 6 and 7 show cross-sectional views taken along the lines VI-VI and VII-VII in

FIG. 2, respectively.

As shown in FIGS. 2 and 6, the port block 20 is provided with a pair of hydraulic oil passages 101 that form the pair of hydraulic oil lines 100 and a charge oil passage 111 that forms the charge line 110, one end of which is fluidly connected to an oil supply source and the other end of which is fluidly connected to the pair of hydraulic oil lines 100 via a pair of check valves 115.

In the present embodiment, as shown in FIG. 3, an auxiliary pump 910 driven by the driving source 900 is employed as the oil supply source.

As shown in FIG. 3, the charge line 110 is set at a predetermined oil pressure by a relief valve 112.

In the present embodiment, as shown in FIG. 3, the pair of hydraulic oil passages 101 are fluidly connected to each other by a communicating oil passage 105 provided with a high-pressure relief valve 106 that acts bidirectionally, and when the oil pressure of one of the pair of hydraulic oil passages 101 exceeds a predetermined oil pressure, hydraulic oil flows into the other hydraulic oil passage 101 from said one hydraulic oil passage 101. This configuration makes it possible to effectively prevent the pair of hydraulic oil passages 101 from reaching an abnormally high pressure.

As shown in FIGS. 1 and 6, the charge oil passage 110 has one end that opens to the external surface to form a charge port 111 a and the other end that branches in two directions to be fluidly connected to the pair of hydraulic oil passages 101 via the pair of check valves 115.

Furthermore, the port block 20 is formed with the oil reservoir space 200 and a first lubricating-oil-supply oil passage 150 having one end fluidly connected to the charge oil passage 111 and the other end fluidly connected to the oil reservoir space 200, as shown in FIG. 1.

The thus configuration in which a part of the oil in the charge line 110 is used as the oil source of the lubricating oil supply structure makes it possible to supply lubricating oil to the first and second axial piston members 60(1) and 60(2) while simplifying the structure.

The lubricating oil supply structure according to the present embodiment is configured to supply a part of the oil in the charge line 110 also to a portion supporting the first swash plate 70(1) that functions as a movable swash plate.

First, the supporting structure of the first swash plate 70(1) will now be described.

As shown in FIGS. 2 and 4, the first swash plate 70(1) has a base portion 75 supported by the first peripheral wall 16(1) in a rotatable manner around the rocking axis R perpendicular to the first rotational shaft 50(1) and a swash plate body 71 supported by the base portion 75 and directly or indirectly engaged with the free ends of the plurality of pistons 62(1).

More specifically, the first peripheral wall 16 is formed with a supporting hole that is coaxially with the rocking axis R, and the base portion 75 is supported by the supporting hole in a rotatable manner around the axis line.

In the present embodiment, as shown in FIGS. 2 and 4, the first swash plate 70(1) is a trunnion-type swash plate.

Therefore, the first swash plate 70(1) has a pair of base portions 75 and 75 disposed on the rocking axis R, with the swash plate body 71 being held therebetween.

That is, as shown in FIGS. 2 and 4, a first side surface of the first peripheral wall 16 that is positioned on one side in the rocking axis R direction is formed with a first supporting hole 16 a coaxial with the rocking axis R, and a second side surface of the first peripheral wall 16 that is positioned on the other side in the rocking axis R direction is formed with a second supporting hole 16 b coaxial with the rocking axis R.

In this configuration, the pair of base portions 75 and 75 are supported in a rotatable manner around the respective axis lines via first and second bearing members 19 a and 19 b inserted into the first and second supporting holes 16 a and 16 b.

The first swash plate 70(1) tilts toward one side and the other side around the rocking axis R by an operating force applied to one of the pair of bases 75 and 75.

As shown in, for example, FIGS. 2 to 4, the axial piston device 1 according to the present embodiment has a hydraulic servomechanism 500 for applying an operating force to the first swash plate 70(1).

A detailed configuration of the hydraulic servomechanism 500 will be described later.

As shown in FIGS. 2 and 4, a first base portion 75 that is one of the pair of base portions 75 and receives an operating force is supported by the corresponding supporting hole 16 a via a connecting coupling 80 in a rotatable manner around the axis line, while a second base portion 75 that is the other one of the pair of base portions 75 is supported by the corresponding supporting hole 16 b via a blocking coupling 85 in a rotatable manner around the axis line.

In the present embodiment, as shown in FIGS. 2 and 4, the first base portion 75 is supported by the first supporting hole 16 a, and the second base portion 75 is supported by the second supporting hole 16 b.

As shown in FIGS. 2 and 4, the connecting coupling 80 has a first cylindrical part 81 inserted into the supporting hole 16 a, and the first base portion 75 is supported by the first cylindrical part 81 via the first bearing member 19 a in a rotatable manner around the axis line.

In the connecting coupling 80, the outer end side of the first cylindrical part 81 is an opening in order to allow access from outside to the first base portion 75.

This opening is blocked by the hydraulic servomechanism 500 that is connected to the first side surface so as to surround the connecting coupling 80.

As shown in FIGS. 2 and 4, the blocking coupling 85 has a second cylindrical part 86 inserted into the supporting hole 16 b and an outer wall part 87 blocking the outer end side of the second cylindrical part 86, and the second base portion 75 is supported by the second cylindrical part 86 via the second bearing member 19 b in a rotatable manner around the axis line.

The lubricating oil supply structure according to the present embodiment has the following configuration in order to supply lubricating oil to the first swash plate 70(1) supported in the above-described manner.

Specifically, the lubricating oil supply structure has a second lubricating-oil-supply oil passage 160 that receives oil from the charge oil passage 111 or the first lubricating-oil-supply oil passage 150.

As shown in FIG. 1, the second lubricating-oil-supply oil passage 160 has a port-block-side supply oil passage 161 formed in the port block 20 and a housing-body-side supply oil passage 165 formed in the first housing body 15(1).

As shown in FIGS. 1 and 6, the port-block-side supply oil passage 161 has one end fluidly connected to the charge oil passage 111 or the first lubricating-oil-supply oil passage 150 and the other end open to a portion in contact with the first peripheral wall 16(1) of the first housing body 15(1).

As shown in FIGS. 1 and 4, with the first housing body 15(1) being connected to the port block 20, the housing-body-side supply oil passage 165 has a peripheral wall oil hole 166 formed in the first peripheral wall 16(1) so as to be fluidly connected to the other end of the port-block-side supply oil passage 161; a first oil hole 167 for the movable swash plate, having one end side fluidly connected to the peripheral wall oil hole 166 and the other end side open to the first supporting hole 16 a to form a discharge end 167 a for the first supporting hole; and a second oil hole 168 for the movable swash plate, having one end side fluidly connected to the peripheral wall oil hole 166 and the other end side open to the second supporting hole 16 b to form a discharge end 168 a for the second supporting hole.

On the other hand, the first cylindrical part 81 of the connecting coupling 80 is provided with a first annular groove 81 a formed in the outer circumferential surface and a first penetrating oil hole 81 b causing the first annular groove 81 a to be fluidly connected to the interior of the first cylindrical part 81.

The second cylindrical part 86 of the blocking coupling 85 is provided with a second annular groove 86 a formed in the outer circumferential surface and a second penetrating oil hole 86 b causing the second annular groove 86 a to be fluidly connected to the interior of the second cylindrical part 86.

The first annular groove 81 a is disposed so as to be fluidly connected to the discharge end 167 a for the first supporting hole, when the connecting coupling 80 is attached to the first supporting hole 16 a.

The second annular groove 86 a is disposed so as to be fluidly connected to the discharge end 168 a for the second supporting hole, when the blocking coupling 85 is attached to the second supporting hole 16 b.

In the present embodiment, the inner diameters of the first and second supporting holes 16 a and 16 b have the same size, and the outer diameters and the inner diameters of the first and second cylindrical parts 81 and 86 have the same sizes, so that it is possible to attach the connecting coupling 80 to the second supporting hole 16 b and the blocking coupling 85 to the first supporting hole 16 a.

Attachment of the connecting coupling 80 to the second supporting hole 16 b causes the first annular groove 81 a to be fluidly connected to the discharge end 168 a for the second supporting hole, and attachment of the blocking coupling 85 to the first supporting hole 16 a causes the second annular groove 86 a to be fluidly connected to the discharge end 167 a for the first supporting hole.

In the present embodiment, as shown in FIG. 4, restrictors are provided in the first and second penetrating oil holes 81 b and 86 b for adjustment of the amounts of lubricating oil to the first and second bearing members 19 a and 19 b.

In the present embodiment, as shown in FIG. 5, the relief valve 112 is attached to the first peripheral wall 16 so as to act on the housing-body-side supply oil passage 165.

As shown in FIGS. 2 and 4, in the present embodiment, the first and second bearing members 19 a and 19 b supporting the pair of bases 75 are tapered bearing members.

In this case, it is necessary to precisely adjust the clearance between the first bearing member 19 a supporting the first base portion 75 and the second bearing member 19 b supporting the second base portion 75.

In this regard, in the present embodiment, the clearance between the pair of first and second bearing members 19 a and 19 b is kept constant by taking advantage of the oil pressure of the charge line 110.

FIG. 8 shows an enlarged view near the blocking coupling 85 shown in FIG. 4.

Specifically, as shown in FIGS. 4 and 8, the axial piston device 1A has a cover plate 30 removably connected to the first housing body 15(1) so as to surround the outer wall part 87 of the blocking coupling 85.

The cover plate 30 and the outer wall part 87 are configured to form an oil chamber 30 a therebetween, with the cover plate 30 being attached to the first housing body 15(1).

Moreover, the first housing body 15(1) and the cover plate 30 are formed with a communicating oil passage 170 having one end side fluidly connected to the housing-body-side supply oil passage 165 and the other end side fluidly connected to the oil chamber 30 a.

Thus, in the present embodiment, the blocking coupling 85 is pressed toward the connecting coupling 80 by taking advantage of the oil pressure of the charge line 110, and thereby the second bearing member 19 b supported by the blocking coupling 85 is pressed toward the first bearing member 19 a supported by the connecting coupling 80, to keep the clearance between the pair of first and second bearing members 19 a and 19 b constant.

Here, the hydraulic servomechanism 500 will now be described.

As shown in FIGS. 2 and 4, the hydraulic servomechanism 500 includes a casing 510, a servo piston 530, a spool 540, an operating member 550, and a link arm 560 for connecting the operating member 550 and the spool 540.

The casing 510 is removably attached to the housing 10.

In the present embodiment, the casing 510 is removably attached to the first side surface of the first peripheral wall 16A of the first housing body 15A so as to surround the connecting coupling 80.

Specifically, bolt holes are formed in the first side surface, and as shown in FIG. 7, through-holes 518 corresponding to the bolt holes are formed in the casing 510, and the casing 510 is removably attached to the first side surface by bolts inserted into the through-holes 518.

As shown in FIG. 7, the casing 510 has an accommodating space 515 that accommodates the servo piston 530.

The servo piston 530 is accommodated in the accommodating space 515 in a reciprocatable manner in the axial direction while defining a first oil chamber 515 a and a second oil chamber 515 b in a fluid tight manner on one end side and the other end side of the accommodating space 515, respectively.

As shown in FIG. 7, the casing 510 also has a spool chamber 520 that accommodates the spool 540.

The spool 540 is slidably accommodated in the spool chamber 520, and is configured to switch between a supply and discharge of pressure oil to and from the first and second oil chambers 515 a and 515 b according to the movement in the spool chamber 520.

Specifically, as shown in FIGS. 3, 4, and 7, the casing 510 is formed with an input oil passage 581 having one end open to the inner surface in contact with the housing body 15 and the other end fluidly connected to an input port 521 of the spool chamber 520, a first oil passage 582 having one end fluidly connected to a first port 522 of the spool chamber 520 and the other end fluidly connected to the first oil chamber 515 a, a second oil passage 583 having one end fluidly connected to a second port 523 of the spool chamber 520 and the other end fluidly connected to the second oil chamber 515 b, and a drain oil passage 584.

In this configuration, the spool 540 can selectively take a first position in which the input port 521 is fluidly connected to the first port 523 and the drain oil passage 584 is fluidly connected to the second port 523, a second position in which the input port 521 is fluidly connected to the second port 523 and the drain oil passage 584 is fluidly connected to the first port 522, and a retaining position in which the first and second ports 522 and 523 are blocked.

The operating member 550 is supported by the casing 510, with one end extending to the outside and the other end being operatively connected to the spool 540.

As shown in FIGS. 2 and 4, in the present embodiment, the operating member 550 is supported in a rotatable manner around an axis line by the casing 510 so as to be parallel to the rocking axis R.

The link arm 560 operatively connects the operating member 550 and the spool 540 such that the spool 540 moves in accordance with the rotation of the operating member 550 around the axis line.

The hydraulic servomechanism 500 is configured such that attachment of the casing 510 to the housing 10 causes the servo piston 530 to be operatively connected to a connecting arm 600 that is connected to the first base portion 75, and the first base portion 75 to be operatively connected to the link arm 560 that is connected to the spool 540.

Specifically, as shown in FIG. 2, the connecting arm 600 has a base end connected to the first base portion 75 and a tip end extending radially outward with reference to the rocking axis R.

The connecting arm 600 is provided with an engagement projection 605 projecting radially outward and an engagement depression 610 depressed radially inward with reference to the axis of the first rotational shaft 50(1).

As shown in FIG. 7, the servo piston 530 has a first and second large-diameter parts 531 and 532 that respectively receive the oil pressures of the first oil chamber 515 a and the second oil chamber 515 b, and a small diameter-part 533 that forms an annular engagement groove 535 between the first and second large-diameter parts 531 and 532 while connecting both large-diameter parts 531 and 532.

The servo piston 530, in a state in which an access to the engagement groove 535 is possible, is accommodated in the accommodating space 515.

Specifically, as shown in FIG. 2, the accommodating space 515 has an access opening 515 a on the side it faces the housing 10 when the casing 510 is attached to the housing 10, enabling an access to the engagement groove 535 via the access opening 515 a.

As shown in FIG. 2, the link arm 560 that operatively connects the operating member 560 and the spool 540 is provided with an engagement projection 565 projecting radially inward with reference to the axis of the first rotational shaft 50(1).

In this configuration, attaching the casing 510 to the housing 10 causes the engagement projection 605 of the connecting arm 600 to engage with the engagement groove 535, and the engagement projection 565 of the link arm 560 to engage with the engagement depression 610.

In the present embodiment, the hydraulic servomechanism 500 is configured to receive a supply of hydraulic oil from the charge line 110.

Specifically, as shown in FIG. 4, the first housing body 15(1) is formed with a supply oil passage 180 for a hydraulic servo. The supply oil passage 180 has one end side fluidly connected to the housing-body-side supply oil passage 165 and the other end side open to a portion of the wall surface of the first housing body 15(1) to which the hydraulic servomechanism 500 is attached to form a servo output port 180 a, is formed in.

The servo output port 180 a is disposed so as to be fluidly connected to the input oil passage 581 when the first housing body 15(1) is attached to the casing 510.

In the present embodiment, as shown in FIG. 7, the servo piston 530 and the spool 540 are disposed such that their axial directions are parallel to each other, and they are movable in the direction (hereinafter referred to as the first direction Dl) perpendicular to the rocking axis R.

As shown in FIG. 7, the link arm 560 and the connecting arm 600 extend in a second direction D2 perpendicular to both the rocking axis R and the first direction D1.

The link arm 560 is operatively connected to the operating member 550 at a first connecting position on one side in the axial direction, operatively connected to the connecting arm 600 at a second connecting position on the other side in the axial direction, and operatively connected to the spool 540 at a third connecting position between the first and second connecting positions.

The hydraulic servomechanism 500 with this configuration operates in the following manner.

When the operating member 550 is operated toward one side around the axis from an initial state in which the operating member 550 is not operated and the servo piston 530 is placed in a neutral position (see FIG. 7), the first connecting position of the link arm 560 moves in a direction corresponding to the direction of operation of the operating member 550, with the second connecting position being substantially fixed. That is, the link arm 560 moves around the second connecting position.

Due to this movement of the link arm 560, the spool 540 moves toward one side in the axial direction and arrives at the first position.

In this state, the first port 522 is fluidly connected to the input port 521, and the second port 523 is fluidly connected to the drain oil passage 584, as described above.

Accordingly, hydraulic oil is supplied to the first oil chamber 515 a and hydraulic oil is discharged from the second oil chamber 515 b, thus the servo piston 530 moves to one side in the axial direction, and, thereby, the first swash plate 70(1) tilts toward one side around the rocking axis (for example, in the direction in which the volume of the first axial piston member 60(1) increases) via the connecting arm 600.

Here, when the connecting arm 600 moves in accordance with the movement of the servo piston 530 toward one side in the axial direction, a portion of the link arm 560 on the side where the second connecting position is located moves in accordance with the movement of the connecting arm 600.

Due to this movement of the link arm 560, the spool 530 moves from the first position to the other side in the axial direction and returns to the retaining position.

Accordingly, the first and second ports 522 and 523 are blocked, and the servo piston 530, i.e., the first swash plate 70(1), is retained in that position.

Thus, in the present embodiment, attaching the casing 510 to the first housing body 15 causes the servo piston 530 to be engaged with the connecting arm 600 connected to the first base portion 75 and also the link arm 560 that operatively connects the operating member 550 and the spool 540 to be engaged with the connecting arm 600, and, on the other hand, removing the casing 510 from the housing body 15 cancels the engagement of the servo piston 530 and the link arm 560 with the connecting arm 600.

It is therefore easy to make a configurational change between a configuration in which the first swash plate 70(1) that functions as a movable swash plate is tilted by the hydraulic servomechanism 500 and a configuration in which it is tilted without using the hydraulic servomechanism 500.

In the present embodiment, with reference to the axis of the first rotational shaft 50(1), the servo piston 530 is formed with the engagement groove 535 that opens radially inward and the connecting arm 600 is formed with the engagement projection 605 that extends radially outward, but as long as the servo piston 530 engages with and disengages from the connecting arm 600 in accordance with the attachment and detachment of the casing 510 to and from the housing 10, the present invention is not limited to this configuration.

That is, it is also possible to provide the servo piston 530 with an engagement projection that extends radially inward and provide the connecting arm 600 with an engaging depression that opens radially outward with reference to the axis of the first rotational shaft 50(1).

Likewise, in the present embodiment, with reference to the axis of the first rotational shaft 50(1), the link arm 560 is provided with an engagement projection 565 that extends radially inward and the connecting arm 600 is provided with an engaging depression 610 that opens radially outward, but, instead, it is also possible to provide the link arm 560 with an engagement depression that opens radially inward and provide the connecting arm 600 with an engaging projection that extends radially outward.

In the present embodiment, as shown in FIG. 4, the other end side of the first oil hole 167 for the movable swash plate opens to the first supporting hole 16 a to serve as the discharge end 167 a for the first supporting hole, the oil supplied from the discharge end 167 a for the first supporting hole via the first annular groove 81 a and the first penetrating oil hole 81 b formed in the connecting coupling 80, which is attached to the first supporting hole 16 a, is used as lubricating oil for the first bearing member 19 a, and the oil discharged from the drain oil passage 584 in the hydraulic servomechanism 500 is also used as lubricating oil for the first bearing member 19 a.

Thus, in the configuration in which the discharge oil from the drain oil passage 584 in the hydraulic servomechanism 500 can be used as lubricating oil for the first bearing member 19 a, the discharge end 167 a for the first supporting hole can be eliminated.

FIG. 9 is a vertical cross-sectional view corresponding to FIG. 4, which is a vertical cross-sectional view of a first modification 1B of the axial piston device.

In the first modification 1B, the same components as those in the axial piston device 1A are given the same reference numbers.

In the first modification 1B shown in FIG. 9, the other end side of the first oil hole 167 for the movable swash plate is fluidly connected to the supply oil passage 180 for the hydraulic servo, but is not open to the first supporting hole 16 a and is blocked.

In the first modification 1B, only the discharge oil from the drain oil passage 584 in the hydraulic servomechanism 500 is used as lubricating oil for the first bearing member 19 a.

Also, the first modification 1B is configured such that the lubricating oil for the second bearing member 19 b is supplied via the oil chamber 30 a.

FIG. 10 shows an enlarged view near the blocking coupling 85 in the first modification 1B.

As shown in FIGS. 9 and 10, the other end side of the second oil hole 168 for the movable swash plate is fluidly connected to the communicating oil passage 170, but is not open to the second supporting hole 16 b and is blocked.

In the first modification 1B, the outer wall part 87 of the blocking coupling 85 is formed with a restrictor-equipped oil hole 175 that supplies some of the oil in the oil chamber 30 a to the second bearing member 19 b while ensuring oil pressure in the oil chamber 30 a.

FIG. 11 shows a partially enlarged cross-sectional view of a second modification 1C of the axial piston device.

In the figure, the same components as those in the axial piston device 1A and the first modification 1B are given the same reference numbers.

In the axial piston device 1A and the first modification 1B, the blocking coupling 85 supporting the second bearing member 19 b is pressed by the oil pressure of the oil chamber 30 a toward the connecting coupling 80 supporting the first bearing member 19 a, to keep the clearance between the pair of first and second bearing members 19 a and 19 b constant.

On the other hand, in the second modification 1C, the blocking coupling 85 is pressed toward the connecting coupling 80 by biasing members that take the form of coned-disc springs 40 as shown in FIG. 11.

Specifically, compared with the axial piston device 1A and the first modification 1B, the second modification 1C has a cover plate 30C in place of the cover plate 30 and further has the coned-disc springs 40.

The coned-disc springs 40 are placed between the outer wall part 87 of the blocking coupling 85 and the cover plate 30C so as to press the blocking coupling 85 toward the connecting coupling 80.

It is also possible to use coil springs 41 in place of the coned-disc springs 40 as the biasing members.

FIG. 12 shows a partially enlarged cross-sectional view of a third modification 1D of the axial piston device in which the coil springs 41 are used as the biasing members.

In the figure, the same components as those in the axial piston device 1A, the first modification 1B, and the second modification 1C are given the same reference numbers.

As shown in FIG. 12, compared with the second modification 1C, the third modification 1D has a cover plate 30D in place of the cover plate 30C and also has the coil springs 41 in place of the coned-disc springs 40.

The coil springs 41 are placed between the outer wall part 87 of the blocking coupling 85 and the cover plate 30D so as to press the blocking coupling 85 toward the connecting coupling 80.

Second Embodiment

Below, another embodiment of a lubricating oil supply structure according to the present invention will now be described with reference to the appended drawings.

FIG. 13 shows a vertical cross-sectional view of one example 2A of an axial piston device to which the lubricating oil supply structure according to the present embodiment is applied.

In the figure, the same components as those in the axial piston device 1A of the first embodiment are given the same reference numbers, and descriptions thereof are omitted if appropriate.

First, the axial piston device 2A will now be described.

In the axial piston device 1A of the first embodiment, the first rotational shaft 50(1) functioning as a pump shaft and the second rotational shaft 50(2) functioning as a motor shaft are coaxially disposed.

On the other hand, in the axial piston device 2A of the present embodiment, the first and second rotational shafts 50(1) and 50(2) are disposed parallel to each other in a mutually displaced state.

Compared with the axial piston member 1A, the axial piston device 2A has a housing 710 in place of the housing 10.

The housing 710 is configured to accommodate the first and second axial piston members 60(1) and 60(2) and, also, support the first rotational shaft 50(1) while defining a first oil reservoir space 200(1) that one end face of the first rotational shaft 50(1) faces and support the second rotational shaft 50(2) while defining a second oil reservoir space 200(2) that one end face of the second rotational shaft 50(2) faces.

Specifically, as shown in FIG. 13, the housing 710 has a housing body 715 provided with openings into which the first and second axial piston members 60(1) and 60(2) can be inserted; a port block 720 removably connected to the housing body 715 so as to block the openings; a first cover 730(1) removably connected to a housing assembly in which the port block 720 and the housing body 715 are connected, so as to form the first oil reservoir space 200(1); and a second cover 730(2) removably connected to the housing assembly so as to form the second oil reservoir space 200(2).

The housing body 715 has a peripheral wall 716 extending in the axial direction of the first and second rotational shafts 50(1) and 50(2) and defining the openings on one end side in the axial direction and an end wall 717 blocking the other end side in the axial direction of the peripheral wall 716.

The respective end sides of the first rotational shaft 50(1) in the axial direction are supported in a rotatable manner around the axis line by the port block 720 and the end wall 717 via bearing members 55 a(1) and 55 b(1).

Likewise, the respective end sides of the second rotational shaft 50(2) in the axial direction are supported in a rotatable manner around the axis line by the port block 720 and the end wall 717 via bearing members 55 a(2) and 55 b(2).

In the present embodiment, the first end side 50 a(1) on one side in the axial direction of the first rotational shaft 50(1) is supported by the port block 720 via the bearing member 55 a(1), and the second end side 50 b(1) on the other side in the axial direction is supported by the end wall 717 via the bearing member 55 b(1).

Also, the first end side 50 a(2) on one side in the axial direction of the second rotational shaft 50(2) is supported by the port block 720 via the bearing member 55 a(2), and the second end side 50 b(2) on the other side in the axial direction is supported by the end wall 717 via the bearing member 55 b(2).

In the present embodiment, the second end side 50 b(1) of the first rotational shaft 50(1) extends outward from the end wall 717 and forms an input end operably driven by the driving source 900 (see FIG. 3), and the first end side 50 a(2) of the second rotational shaft 50(2) extends outward from the port block 720 and forms an output end.

As shown in FIG. 13, in the present embodiment, the axial piston device 2A integrally has an auxiliary pump 910 that is driven by the first rotational shaft 50(1) functioning as a pump shaft and that functions as a charge pump, and an auxiliary-pump case 915 connected to the housing assembly so as to surround the auxiliary pump 910 functions as the first cover 730(1).

In the present embodiment, as shown in FIG. 13, the first end side 50 a(1) of the first rotational shaft 50(1) extends more outward than the port block 720, and the auxiliary pump 910 is driven by the outward-extending part of the first end side 50 a(1).

The auxiliary-pump case 915 that functions as the first cover 730(1) is connected to the port block 720 so as to surround the auxiliary pump 910 and the outward-extending part of the first end side 50 a(1) of the first rotational shaft 50(1), while defining the first oil reservoir space 200(1) between the auxiliary-pump case 915 and the end face on the first end side 50 a(1) of the first rotational shaft 50(1).

On the other hand, the second cover 730(2) is connected to the end wall 717, while forming the second oil reservoir space 200(2) between the second cover 730(2) and the end face on the second end side 50 b(2) of the second rotational shaft 50(2).

Specifically, the second end side 50 b(2) of the second rotational shaft 50(2) is supported by the end wall 717, with the end face being exposed to the outside.

The second cover 730(2) is connected to the end wall 717, while defining the second oil reservoir space 200(2) between the second cover 730(2) and the end face on the second end side 50 b(2) of the second rotational shaft 50(2).

Here, the lubricating oil supply structure according to the present embodiment will now be described.

As shown in FIG. 13, the lubricating oil supply structure has the first oil reservoir space 200(1) facing the end face on one side of the first rotational shaft 50(1) while being capable of receiving oil from an oil source, a first-rotational-shaft-side supply oil passage 211(1) formed in the first rotational shaft 50(1), the second oil reservoir space 200(2) facing the end face on one side of the second rotational shaft 50(2) while being capable of receiving oil from an oil source, and a second-rotational-shaft-side supply oil passage 211(2) formed in the second rotational shaft 50(2).

The first-rotational-shaft-side supply oil passage 211(1) has a first axial hole 215(1) open to the end face on the first end side that faces the first oil reservoir space 200(1) among the two end faces of the first rotational shaft 50(1), and a first-axial-piston-member lubricating oil hole 220(1) having one end fluidly connected to the first axial hole 215(1) and the other end open to the external surface of the first rotational shaft 50(1) toward the first axial piston member 60(1).

The second-rotational-shaft-side supply oil passage 211(2) has a second axial hole 215(2) open to the end face on the second end side that faces the second oil reservoir space 200(2) among the two end faces of the second rotational shaft 50(2), and a second-axial-piston-member lubricating oil hole 220(2) having one end fluid-connected to the second axial hole 215(2) and the other end open to the external surface of the second rotational shaft 50(2) toward the second axial piston member 60(2).

Thus, in the present embodiment as well, the first and second axial holes 215(1) and 215(2) respectively formed in the first and second rotational shafts 50(1) and 50(2) open to the end faces facing the first and second oil reservoir spaces 200(1) and 200(2), and lubricating oil flows into the first and second axial holes 215(1) and 215(2) from the corresponding first and second oil reservoir spaces 200(1) and 200(2).

Therefore, centrifugal force caused by the axial rotation of the first and second rotational shafts 50(1) and 50(2) does not interfere with the flow of lubricating oil, and the lubricating oil is allowed to smoothly flow to the first and second axial piston members 60(1) and 60(2).

In the present embodiment, as shown in FIG. 13, the first-rotational-shaft-side supply oil passage 211(1) further has a first-end-side lubricating oil hole 225 a(1) having one end fluidly connected to the first axial hole 215(1) and the other end open to a portion of the external surface of the first rotational shaft 50(1) located in the first-rotational-shaft first-end-side bearing hole 18 a(1), and is configured to supply lubricating oil also to a bearing member 55 a(1) that supports the first end side 50 a(1) of the first rotational shaft 50(1).

The configuration for supplying lubricating oil to the bearing member 55 b(1) that supports the second end side 50 b(1) of the first rotational shaft 50(1) will be described later.

On the other hand, in the present embodiment, the second-rotational-shaft-side supply oil passage 211(2) further has a first-end-side lubricating oil hole 225 a(2) having one end fluidly connected to the second axial hole 215(2) and the other end open to a portion of the external surface of the second rotational shaft 50(2) located in the second-rotational-shaft first-end-side bearing hole 18 a(2) and a second-end-side lubricating oil hole 225 b(2) having one end fluidly connected to the second axial hole 215(2) and the other end open to a portion of the external surface of the second rotational shaft 50(2) located in the second-rotational-shaft second-end-side bearing hole 18 b(2), and is configured to supply lubricating oil also to bearing members 55 a(2) and 55 b(2) that respectively support the first and second end sides 50 a(2) and 50 b(2) of the second rotational shaft 50(2), as shown in FIG. 13.

Next, the oil source for the lubricating oil supply structure will now be described.

In the present embodiment, the auxiliary pump 910 is used as an oil source for the lubricating oil supply structure.

Specifically, the housing 710 is formed with a first lubricating-oil-supply oil passage 750 having one end side fluidly connected to the discharge side of the auxiliary pump 910 and the other end side fluidly connected to the first oil reservoir space 200(1) and a second lubricating-oil-supply oil passage 760 having one end side fluidly connected to the discharge side of the auxiliary pump 910 and the other end side fluidly connected to the second oil reservoir space 200(2).

As shown in FIG. 13, the first lubricating-oil-supply oil passage 750 is formed in the first cover 730(1).

On the other hand, the second lubricating-oil-supply oil passage 760 has a port-block-side supply oil passage 761 formed in the port block 720 and a housing-body-side supply oil passage 765 formed in the housing body 715.

The port-block-side supply oil passage 761 has one end side fluidly connected to the discharge side of the auxiliary pump 910 via the charge oil passage 111 and the other end side open to the portion in contact with the peripheral wall 716 of the housing body 715.

Specifically, as shown in FIG. 13, the port block 720 is formed with a charge oil passage 111 having one end side fluidly connected to the discharge side of the auxiliary pump 910 and the other end side fluidly connected to the pair of hydraulic oil passages 101 (not shown in FIG. 13) via the check valves 115 (not shown in FIG. 13).

One end side of the port-block-side supply oil passage 761 is fluidly connected to the charge oil passage 111.

As shown in FIG. 13, the housing-body-side supply oil passage 765 has a peripheral wall oil hole 766 formed in the peripheral wall 716 so as to be fluidly connected to the other end of the port-block-side supply oil passage 761 in a state where the housing body 715 is connected to the port block 720, and an end wall oil hole 767 formed in the end wall 717 so as to have one end side fluidly connected to the peripheral wall oil hole 766 and the other end side fluidly connected to the second oil reservoir space 200(2).

In this configuration, the end wall 717 is formed with an oil hole 780 having one end side fluidly connected to the end wall oil hole 767 and the other end side open toward the bearing member 55 b(1) supporting the second end side 50 b(1) of the first rotational shaft 50(1), so that the oil in the housing-body-side supply oil passage 765 is supplied via the oil hole 780 as lubricating oil for the bearing member 55 b(1).

In the present embodiment, as shown in FIG. 13, the end wall oil hole 767 has a first portion 767 a fluidly connected to the peripheral wall oil hole 766 and a second portion 767 b fluidly connected to the second oil reservoir space 200(2), and the first and second portions 767 a and 767 b are fluidly connected to each other via an annular groove 51 formed in a portion of the external surface of the first rotational shaft 50(1) located in the first-rotational-shaft second-end-side bearing hole 18 b(1). 

What is claimed is:
 1. A lubricating oil supply structure applicable to an axial piston device including a rotational shaft, an axial piston member supported by the rotational shaft in a relatively non-rotatable manner with respect thereto and a housing accommodating the axial piston member wherein the rotational shaft supports the axial piston device at a central part in an axial direction and is supported at one end side and the other end side in the axial direction by first-end-side and second-end-side bearing holes formed in the housing in a rotatable manner around the axis line, the lubricating oil supply structure comprising, an oil reservoir space formed in the housing so as to be capable of receiving oil from an oil source and face at least one of the two end faces in the axial direction of the rotational shaft, and a rotational-shaft-side supply oil passage that is formed in the rotational shaft, wherein the rotational-shaft-side supply oil passage has an axial hole open to an end face of the rotational shaft that faces the oil reservoir space among the two end faces in the axial direction of the rotational shaft and an axial-piston-member lubricating oil hole having one end fluidly connected to the axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the axial piston member.
 2. The lubricating oil supply structure according to claim 1, wherein the rotational-shaft-side supply oil passage has a lubricating oil hole for bearing member having one end fluidly connected to the axial hole and the other end open to at least one of portions of the external surface of the rotational shaft that are located in the first- and second-end-side bearing holes, respectively.
 3. The lubricating oil supply structure according to claim 2, wherein the lubricating oil hole for bearing member includes a first-end-side lubricating oil hole that is fluidly connected to the axial hole and open to the portion of the external surface of the rotational shaft located in the first-end-side bearing hole, and a second-end-side lubricating oil hole that is fluidly connected to the axial hole and open to the portion of the external surface of the rotational shaft located in the second-end-side bearing hole.
 4. The lubricating oil supply structure according to claim 3, wherein the rotational shaft includes first and second rotational shafts coaxially disposed to each other, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the first and second rotational shafts are disposed such that there is a gap between the end face on the first end side of the first rotational shaft and the end face on the second end side of the second rotational shaft, the gap being used as the oil reservoir space, wherein the axial hole includes first and second axle holes that are fluidly connected to the oil reservoir space and formed in the first and second rotational shafts, respectively, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member, and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 5. The lubricating oil supply structure according to claim 3, wherein the rotational shaft includes first and second rotational shafts arranged parallel to each other to have axis lines mutually displaced, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the oil reservoir space includes a first oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the first rotational shaft, and a second oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the second rotational shaft, wherein the axial hole includes a first axle hole formed in the first rotational shaft so as to be fluidly connected to the first oil reservoir space and a second axle hole formed in the second rotational shaft so as to be fluidly connected to the second oil reservoir space, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 6. The lubricating oil supply structure according to claim 2, wherein the rotational shaft includes first and second rotational shafts coaxially disposed to each other, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the first and second rotational shafts are disposed such that there is a gap between the end face on the first end side of the first rotational shaft and the end face on the second end side of the second rotational shaft, the gap being used as the oil reservoir space, wherein the axial hole includes first and second axle holes that are fluidly connected to the oil reservoir space and formed in the first and second rotational shafts, respectively, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member, and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 7. The lubricating oil supply structure according to claim 2, wherein the rotational shaft includes first and second rotational shafts arranged parallel to each other to have axis lines mutually displaced, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the oil reservoir space includes a first oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the first rotational shaft, and a second oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the second rotational shaft, wherein the axial hole includes a first axle hole formed in the first rotational shaft so as to be fluidly connected to the first oil reservoir space and a second axle hole formed in the second rotational shaft so as to be fluidly connected to the second oil reservoir space, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 8. The lubricating oil supply structure according to claim 1, wherein the rotational shaft includes first and second rotational shafts coaxially disposed to each other, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the first and second rotational shafts are disposed such that there is a gap between the end face on the first end side of the first rotational shaft and the end face on the second end side of the second rotational shaft, the gap being used as the oil reservoir space, wherein the axial hole includes first and second axle holes that are fluidly connected to the oil reservoir space and formed in the first and second rotational shafts, respectively, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member, and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 9. The lubricating oil supply structure according to claim 8, wherein the housing has a port block including the reservoir space, a first housing body removably connected to the port block to form a first accommodating space accommodating the first axial piston member, and a second housing body removably connected to the port block to form a second accommodating space that is positioned opposite to the first accommodating space with reference to the port block and accommodates the second axial piston member.
 10. The lubricating oil supply structure according to claim 8, wherein the first rotational shaft functions as a pump shaft that is operatively connected to a driving source, and the second rotational shaft functions as a motor shaft that outputs rotative power, wherein at least one of the first axial piston member functioning as a hydraulic pump and the second axial piston member functioning as a hydraulic motor is a variable-volume type, wherein the housing is formed with a pair of hydraulic oil passages that fluidly connects the first and second axial piston members so as to form a closed circuit including them, and a charge oil passage for replenishing the closed circuit with hydraulic oil, and wherein a part of oil in the charge oil passage is supplied to the oil reservoir space.
 11. The lubricating oil supply structure according to claim 10, wherein the first axial piston member includes a first cylinder block supported by the first rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the first rotational shaft, and a plurality of first pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of first pistons being directly or indirectly come into contact with a first swash plate provided in the first axial piston device to define the volume of the first axial piston member, wherein the second axial piston member includes a second cylinder block supported by the second rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the second rotational shaft, and a plurality of second pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of second pistons being directly or indirectly come into contact with a second swash plate provided in the second axial piston device to define the volume of the second axial piston member, wherein the other end of the first-axial-piston-member lubricating oil hole is open to a portion of the external surface of the first rotational shaft that is close to a region where the free ends of the plurality of first pistons are come into contact with the first movable swash plate, and wherein the other end of the second-axial-piston-member lubricating oil hole is open to a portion of the external surface of the second rotational shaft that is close to a region where the free ends of the plurality of second pistons are come into contact with the second movable swash plate.
 12. The lubricating oil supply structure according to claim 8, wherein the first axial piston member includes a first cylinder block supported by the first rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the first rotational shaft, and a plurality of first pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of first pistons being directly or indirectly come into contact with a first swash plate provided in the first axial piston device to define the volume of the first axial piston member, wherein the second axial piston member includes a second cylinder block supported by the second rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the second rotational shaft, and a plurality of second pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of second pistons being directly or indirectly come into contact with a second swash plate provided in the second axial piston device to define the volume of the second axial piston member, wherein the other end of the first-axial-piston-member lubricating oil hole is open to a portion of the external surface of the first rotational shaft that is close to a region where the free ends of the plurality of first pistons are come into contact with the first movable swash plate, and wherein the other end of the second-axial-piston-member lubricating oil hole is open to a portion of the external surface of the second rotational shaft that is close to a region where the free ends of the plurality of second pistons are come into contact with the second movable swash plate.
 13. The lubricating oil supply structure according to claim 12, wherein the first swash plate is a movable swash plate including a base portion supported by the housing in a rotatable manner around a rocking axis perpendicular to the first rotational shaft, and a swash plate body supported by the base portion and directly or indirectly engaged with the free ends of the plurality of first pistons, and wherein the housing is formed with a lubricating oil hole for the first swash plate having one end side fluidly connected to the oil source and the other end side open to a supporting hole that is formed in the housing so as to support the base portion.
 14. The lubricating oil supply structure according to claim 1, wherein the rotational shaft includes first and second rotational shafts arranged parallel to each other to have axis lines mutually displaced, wherein the axial piston member includes first and second axial piston members supported by the first and second rotational shafts, respectively, wherein the oil reservoir space includes a first oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the first rotational shaft, and a second oil reservoir space formed in the housing so as to be capable of receiving an oil from the oil source and face at least one of the end faces on one side and the other side in the axis direction of the second rotational shaft, wherein the axial hole includes a first axle hole formed in the first rotational shaft so as to be fluidly connected to the first oil reservoir space and a second axle hole formed in the second rotational shaft so as to be fluidly connected to the second oil reservoir space, and wherein the axial-piston-member lubricating oil hole includes a first-axial-piston-member lubricating oil hole having one end fluidly connected to the first axial hole and the other end open to a portion of the external surface of the first rotational shaft that faces the first axial piston member and a second-axial-piston-member lubricating oil hole having one end fluidly connected to the second axial hole and the other end open to a portion of the external surface of the second rotational shaft that faces the second axial piston member.
 15. The lubricating oil supply structure according to claim 14, wherein the housing includes a port block and a housing body removably connected to the port block to form an accommodating space accommodating the first and second axial piston members.
 16. The lubricating oil supply structure according to claim 14, wherein the first rotational shaft functions as a pump shaft that is operatively connected to a driving source, and the second rotational shaft functions as a motor shaft that outputs rotative power, wherein at least one of the first axial piston member functioning as a hydraulic pump and the second axial piston member functioning as a hydraulic motor is a variable-volume type, wherein the housing is formed with a pair of hydraulic oil passages that fluidly connects the first and second axial piston members so as to form a closed circuit including them, and a charge oil passage for replenishing the closed circuit with hydraulic oil, and wherein a part of oil in the charge oil passage is supplied to the oil reservoir space.
 17. The lubricating oil supply structure according to claim 14, wherein the first axial piston member includes a first cylinder block supported by the first rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the first rotational shaft, and a plurality of first pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of first pistons being directly or indirectly come into contact with a first swash plate provided in the first axial piston device to define the volume of the first axial piston member, wherein the second axial piston member includes a second cylinder block supported by the second rotational shaft in a relatively non-rotatable manner with respect thereto and having a plurality of cylinder holes arranged around the axis line of the second rotational shaft, and a plurality of second pistons accommodated in the plurality of the cylinder holes in a reciprocating manner, free ends of the plurality of second pistons being directly or indirectly come into contact with a second swash plate provided in the second axial piston device to define the volume of the second axial piston member, wherein the other end of the first-axial-piston-member lubricating oil hole is open to a portion of the external surface of the first rotational shaft that is close to a region where the free ends of the plurality of first pistons are come into contact with the first movable swash plate, and wherein the other end of the second-axial-piston-member lubricating oil hole is open to a portion of the external surface of the second rotational shaft that is close to a region where the free ends of the plurality of second pistons are come into contact with the second movable swash plate. 